Authors:
Stuart Reges, Marty Stepp
Chapter:
Inheritance And Interfaces
Exercise:
Exercises
Question:16 | ISBN:9780136091813 | Edition: 2
Question
Declare an interface called Incrementable which represents items that store an integer that can be incremented in some way. The interface has a method called increment that increments the value and a method called getValue that returns the value. Once you have written the interface, write two classes called SequentialIncrementer and RandomIncrementer that implement the interface. The SequentialIncrementer begins its value at 0 and increases it by 1 each time it is incremented. The RandomIncrementer begins its value at a random integer and
changes it to a new random integer each time it is incremented.
Answer
Incrementable.java
public interface Incrementable
{
public void increment();
public int getValue();
}
SequentialIncrementer.java
public class SequentialIncrementer implements Incrementable
{
private int value;
public SequentialIncrementer()
{
value = 0;
}
public SequentialIncrementer(int v)
{
value = v;
}
@Override
public void increment()
{
value += 1;
}
@Override
public int getValue()
{
return value;
}
}
RandomIncrementer.java
public class RandomIncrementer implements Incrementable
{
private int value;
public RandomIncrementer()
{
value = 0;
}
public RandomIncrementer(int v)
{
value = v;
}
@Override
public void increment()
{
value += (int)(Math.random() * 10);
}
@Override
public int getValue()
{
return value;
}
}
Ch09Ex16
public class Ch09Ex16
{
public static void main(String[] args)
{
Incrementable si = new SequentialIncrementer();
System.out.println("Initial value of SequentialIncrementer: " + si.getValue());
si.increment();
si.increment();
System.out.println("After two increments, new value of SequentialIncrementer: " + si.getValue());
Incrementable ri = new RandomIncrementer();
System.out.println("\nInitial value of RandomIncrementer: " + ri.getValue());
ri.increment();
ri.increment();
System.out.println("After two increments, new value of RandomIncrementer: " + ri.getValue());
}
}
Output:
Initial value of SequentialIncrementer: 0
After two increments, new value of SequentialIncrementer: 2
Initial value of RandomIncrementer: 0
After two increments, new value of RandomIncrementer: 7